Re: [linux-pm] Re: [RFC][PATCH -mm 3/4] Hibernation: Pass CR3 in the image header on x86_64

[Rafael J. Wysocki]

On Wednesday, 22 August 2007 18:17, Rafael J. Wysocki wrote:
> On Wednesday, 22 August 2007 10:28, Pavel Machek wrote:
> > Hi!
> > 
> > > From: Rafael J. Wysocki <rjw@xxxxxxx>
> > > 
> > > Since we already pass the address of restore_registers() in the image header,
> > > we can also pass the value of the CR3 register from before the hibernation in
> > > the same way.  This will allow us to avoid using init_level4_pgt page tables
> > > during the restore.
> > > 
> > > Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> > 
> > > @@ -253,10 +262,13 @@ int arch_hibernation_header_save(void *a
> > >  {
> > >  	struct restore_data_record *rdr = addr;
> > >  
> > > -	if (max_size < sizeof(struct restore_data_record))
> > > +	if (max_size < sizeof(*rdr))
> > >  		return -EOVERFLOW;
> > >  	rdr->jump_address = restore_jump_address;
> > > -	rdr->control = (restore_jump_address ^ RESTORE_MAGIC);
> > > +	rdr->cr3 = restore_cr3;
> > > +	rdr->magic = RESTORE_MAGIC;
> > > +	rdr->crc = 0;
> > > +	rdr->crc = crc32_le(0, addr, sizeof(*rdr));
> > >  	return 0;
> > >  }
> > 
> > No, I do not think I like that. I believe both -> control and -> crc
> > is just useless paranoia. Bitflip in this area is not going to be any
> > worse than bitflip anywhere else, we should not pretend this is
> > somehow "more important".
> > 
> > -> control should really be "protocol version"... probably should
> > contain some field that is easy to increment.
> 
> OK
> 
> Perhaps I'll just remove the crc field.

Like in the patch below.

---
From: Rafael J. Wysocki <rjw@xxxxxxx>

Since we already pass the address of restore_registers() in the image header,
we can also pass the value of the CR3 register from before the hibernation in
the same way.  This will allow us to avoid using init_level4_pgt page tables
during the restore.

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
 arch/x86_64/kernel/suspend.c     |   17 +++++++++++++----
 arch/x86_64/kernel/suspend_asm.S |    8 +++++---
 2 files changed, 18 insertions(+), 7 deletions(-)

Index: linux-2.6.23-rc3/arch/x86_64/kernel/suspend.c
===================================================================
--- linux-2.6.23-rc3.orig/arch/x86_64/kernel/suspend.c
+++ linux-2.6.23-rc3/arch/x86_64/kernel/suspend.c
@@ -9,6 +9,7 @@
 
 #include <linux/smp.h>
 #include <linux/suspend.h>
+#include <linux/crc32.h>
 #include <asm/proto.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -150,6 +151,12 @@ extern int restore_image(void);
  */
 unsigned long restore_jump_address;
 
+/*
+ * Value of the cr3 register from before the hibernation (this value is passed
+ * in the image header).
+ */
+unsigned long restore_cr3;
+
 pgd_t *temp_level4_pgt;
 
 static int res_phys_pud_init(pud_t *pud, unsigned long address, unsigned long end)
@@ -239,7 +246,8 @@ int pfn_is_nosave(unsigned long pfn)
 
 struct restore_data_record {
 	unsigned long jump_address;
-	unsigned long control;
+	unsigned long cr3;
+	unsigned long magic;
 };
 
 #define RESTORE_MAGIC	0x0123456789ABCDEFUL
@@ -256,7 +264,8 @@ int arch_hibernation_header_save(void *a
 	if (max_size < sizeof(struct restore_data_record))
 		return -EOVERFLOW;
 	rdr->jump_address = restore_jump_address;
-	rdr->control = (restore_jump_address ^ RESTORE_MAGIC);
+	rdr->cr3 = restore_cr3;
+	rdr->magic = RESTORE_MAGIC;
 	return 0;
 }
 
@@ -270,7 +279,7 @@ int arch_hibernation_header_restore(void
 	struct restore_data_record *rdr = addr;
 
 	restore_jump_address = rdr->jump_address;
-	return (rdr->control == (restore_jump_address ^ RESTORE_MAGIC)) ?
-			0 : -EINVAL;
+	restore_cr3 = rdr->cr3;
+	return (rdr->magic == RESTORE_MAGIC) ? 0 : -EINVAL;
 }
 #endif /* CONFIG_HIBERNATION */
Index: linux-2.6.23-rc3/arch/x86_64/kernel/suspend_asm.S
===================================================================
--- linux-2.6.23-rc3.orig/arch/x86_64/kernel/suspend_asm.S
+++ linux-2.6.23-rc3/arch/x86_64/kernel/suspend_asm.S
@@ -39,6 +39,9 @@ ENTRY(swsusp_arch_suspend)
 	/* save the address of restore_registers */
 	movq	$restore_registers, %rax
 	movq	%rax, restore_jump_address(%rip)
+	/* save cr3 */
+	movq	%cr3, %rax
+	movq	%rax, restore_cr3(%rip)
 
 	call swsusp_save
 	ret
@@ -66,6 +69,7 @@ ENTRY(restore_image)
 
 	/* prepare to jump to the image kernel */
 	movq	restore_jump_address(%rip), %rax
+	movq	restore_cr3(%rip), %rbx
 
 	/* copy image data to their original locations */
 	xorq	%r10, %r10
@@ -116,9 +120,7 @@ ENTRY(restore_registers)
 	movsq
 
 	/* go back to the original page tables */
-1:	movq    $(init_level4_pgt - __START_KERNEL_map), %rax
-	addq    phys_base(%rip), %rax
-	movq    %rax, %cr3
+1:	movq    %rbx, %cr3
 
 	/* Flush TLB, including "global" things (vmalloc) */
 	movq	mmu_cr4_features(%rip), %rax
-
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